1. Field of the Invention
The present invention relates to stable dispersions obtained from the in situ reaction between carbon dioxide and an amine in the presence of a continuous phase carrier; to cellular and microcellular compositions obtainable from these dispersions; and to specific methods for making the dispersions. In particular, the invention relates to solid phase urea group-containing amine/carbon dioxide condensation adducts obtained under specific reaction conditions and dispersed in a continuous phase carrier, the urea group-containing stable dispersion being employed in the formation of foams and microcellular products.
2. Description of the Prior Art
It is known that the physical properties of foams can be altered by using urea or polyisocyanurate dispersions, or polymer modified polyols in the urethane forming process. Common examples of polymer modified polyols are those prepared by the in situ polymerization of a vinyl monomer in the presence of a polyether or polyester polyol as described in U.S. Pat. Nos. 3,652,639; 3,823,201; and 4,690,956. Examples of polyisocyanurate dispersions, optionally containing pendant urea groups, are described in U.S. Pat. Nos. 4,359,541, 4,386,167, and 4,326,043, and are generally prepared by polymerizing a polyisocyanate with a trimerization catalyst, deactivating the catalyst, reacting the free isocyanate groups with an active hydrogen compound such as an amine, and subsequently dispersing the product in the desired polyol. In this method, an amine is reacted with isocyanate and requires one to add the product to a polyol. It is also known that urea based dispersions may be obtained by the reaction of polyisocyanates with a polyamine and/or hydrazines and/or hydrazides as described in U.S. Pat. No. 4,042,537.
Other dispersions include polyisocyanate polyaddition based dispersions of the kind described in U.S. Pat. Nos. 4,374,209 and 4,093,569 formed by reacting an isocyanate with an alkanolamine in the presence of a polyol.
Carbamates of amines formed by the reaction between mono or polyfunctional amines with carbon dioxide at room temperature and atmospheric pressure are described in "The Chemical Structure of Some Diamine Carbamates," 73 J. Am. Chem. Soc. 1829 (1951). In particular, the carbamates described in this article are ammonium salts of alkylcarbamic acid. These amine carbamates are prepared at room temperature and atmospheric pressure in cold alcoholic solutions such as methanol, which is subsequently evaporated to eventually yield a dry carbamate powder. Carbamates prepared by this procedure find use as sources of carbon dioxide in plastic foams as described in U.S. Pat. No. 3,502,600. This patent teaches the formation of a plastic foam by combining an aqueous plastics dispersion of, for example, vinyl acetate with a compound having CH acidic hydrogens adjacent to a carbonyl or nitrilo group, and a pre-formed carbamate prepared by the procedure described in the journal article quoted above, and to this mixture is added an aldehyde which chemically reacts with and disassociates the carbamate to release carbon dioxide. Thus, there no longer remains solid particles in the foam since the carbamate was made to decompose by the addition of an aldehyde and to release carbon dioxide as a blowing agent for foaming action rather than remain as a carbamate dispersion.
Other patents have described the reaction of specific amines with carbon dioxide for the production of polyurethane foams. U.S Pat. Nos. 4,735,970 and 4,500,656 teach one to react an alkanolamine with carbon dioxide in the presence of a polyol to form a homogeneous mixture of an ammonium salt of an alkylcarbamic acid, or an amine/carbon dioxide adduct, and the polyol. U.S. Pat. No. 4,077,920 teaches one to form a carbamate-amine dispersion by bubbling carbon dioxide through an alkanolamine/polyol mixture, and compares the flame retardant properties of foams prepared by this dispersion with a foam prepared by a dispersion of carbamate-amines obtained by reacting an amine without hydroxyl groups and carbon dioxide. This reference, however, does not teach one to react an amine without hydroxyl groups with carbon dioxide at super-atmospheric pressures in the presence of a polyol to produce urea group-containing dispersions.
Finally, U.S. Pat. No. 4,994,503 teaches to improve the impact strength and flexural modulus of a foam by contacting a carbonyl compound, such as a urea, with a polyamine in the presence of a polyahl at atmospheric pressure, or reduced pressure, to produce aminocarbonyl dispersions.